1. Field of the Invention
The present invention relates to an ultrasonic motor.
2. Description of the Related Art
Recently, a small-size, high-torque, long-stroke and high-resolution ultrasonic motor has been frequently used compared with an electromagnetic motor. For example, Jpn. Pat. Appln. KOKAI Publication No. 2005-65358 discloses an ultrasonic motor using a stacked piezoelectric device as the foregoing ultrasonic motor.
Specifically, in order to realize high efficiency, the ultrasonic motor disclosed in the foregoing Publication No. 2005-65358 is provided with an external electrode, which short-circuits an internal electrode. The external electrode is located on both ends (that is, two surfaces) of the longitudinal axis in the stacked piezoelectric device to avoid the vicinity of the middle of flexural vibration in a stacked piezoelectric device.